Spatial Analysis

Visualizing Oil Spill Incidents in California (2008)

# Read in CA county outlines
ca_counties <- read_sf(here("ca_counties","CA_Counties_TIGER2016.shp"))

# Only keep required attributes
ca_subset <- ca_counties %>% 
  select(NAME, ALAND) %>% 
  rename(county_name = NAME, land_area = ALAND)

# Check CRS in console

# Read in oil spill data
oil_spill <- read_sf(here("Oil_Spill_Incident_Tracking","Oil_Spill_Incident_Tracking_%5Bds394%5D.shp"))

# Check CRS in console

Interactive tmap showing the oil spill incidents in California

# Make exploratory tmap

# Set viewing mode to interactive
tmap_mode(mode = "view")

tm_shape(ca_subset) +
  tm_fill() +
  tm_shape(oil_spill) +
  tm_dots()

Figure 1. Inland oil spill incidents in California (2008). Most spills are concentrated in central and southern California.

Chloropleth map showing the counts of oil spill incidents by county

# Join datasets
ca_oil_spill <- ca_subset %>% 
  st_join(oil_spill)

# Find the counts
oil_spill_counts <- ca_oil_spill %>% 
  count(county_name)

# Make chloropleth map
ggplot(data = oil_spill_counts) +
  geom_sf(aes(fill = n), color = "white", size = 0.1) +
  scale_fill_gradientn(colors = c("lightyellow", "orange", "red")) +
  theme_void() +
  labs(fill = "Number of Oil Spill Incidents")

Figure 2. Chloropleth map showing the number of oil spill incidents by county in 2008. Los Angeles county seems to have the highest number of oil spills incidents.